Providing a reliable and low cost method of attaching a mounting bracket to a driver side airbag inflator that allows greater flexibility in the design of the mounting bracket and inflator would be useful.
Inflators are used in airbag module assemblies that are in turn used in inflatable restraint systems. Inflatable restraint systems are employed in automobiles for protecting an occupant against injury by physically restraining the occupant's body when the automobile encounters a collision.
The airbag module assembly normally includes an inflator, a module base plate and an airbag cushion. The inflator includes an inflator housing containing a gas generant material that, once triggered by a remote collision sensor, provides the inflation gas for inflating the airbag cushion. A commonly used inflator housing has a cylindrical sidewall forming a plurality of gas exhaust ports, and an integral annular support that extends radially outwardly from the sidewall below the gas exhaust ports. The module base plate has an inflator-receiving hole with a portion of the sidewall containing the gas exhaust ports extending therethrough with the annular support positioned against the base plate. The airbag cushion has an open mouth formed by a collar that fits over the inflator with the collar positioned against the base plate so that the gas exhaust ports are located within the open mouth. The collar of the airbag cushion and the annular support of the inflator are secured to the module base plate, holding the assembly together, and preventing the airbag cushion and inflator from becoming separated during inflation of the airbag cushion.
Providing a annular support that is separate from, yet easily attachable to the inflator would save manufacturing time and reduce costs. Because the annular support is integral with the inflator housing on most existing inflators, the inflator housing is much more difficult and costly to fabricate. Using a stamping technique to manufacture the inflator, which is preferable from a cost standpoint, does not readily allow incorporating the annular support as an integral part of the inflator. Accordingly, providing an inflator housing that does not have an integral peripheral mounting bracket but has a separate, attachable mounting bracket that can be easily attached to the inflator prior to installing the inflator within the airbag module assembly would be useful.
One prior art inflator, shown and described in U.S. Pat. No. 5,275,431, provides an inflator and a separate retainer member or mounting bracket that is secured to the inflator using a radial crimping or forming method. The '431 inflator has an inflator flange and the mounting bracket has an annular wall surface or cylindrical sleeve encircling the inflator and the inflator flange. A first flange or annular support, that attaches to the airbag module, extends outwardly from the sleeve and a second flange or clamping band extends inwardly over the inflator flange. Once slid onto the inflator flange and the inflator, a crimped portion or flange seat is formed in the sleeve using a radial crimping or forming method. The flange seat clamps the inflator flange against the clamping band securing the mounting bracket to the inflator.
The radial crimping or forming method used to assemble the '431 inflator has many drawbacks. First, radial crimping is an awkward and time consuming assembly method. In addition, radial crimping requires a mounting bracket design that provides a minimum distance between the annular support and the clamping band to allow room for the radial crimping tool. This requirement limits the design options of the mounting bracket and inflator which is significant since a continuing design goal is to minimize this distance to meet size limitations placed on an airbag module adapted to be mounted in a steering wheel.
It would be useful, therefore, to provide a simple, reliable and low cost method of attaching a mounting bracket to a driver side airbag inflator that allows flexibility in the design of the mounting bracket and inflator. The mounting bracket should lock onto the inflator, mount the inflator within an airbag module assembly, and prevent inflator rotation with respect to the bracket. The bracket should secure the inflator to the airbag module assembly, withstand the expansive forces during inflation of the airbag, and provide shake and rattle-free mounting.